Bug or possible problem with Proxy (Squid)

[peruvichito2014]

Hi Gurus
Testing some functions of the Proxy Server (Squid Cache: Version 2.7.STABLE9) –> "Local User"
I added two user, For example user1 and password user1, and user2 and password user2. So In this case when my customer try to connect using the proxy, appear a prompt where they must be fill the user and the password
This option is function correctly.

The problem appear when I delete both user in the Local User (but not appear the option apply like any other labels).
In the desktop of my customer, always appear  a prompt where If they no fill with user1 or user2 (with their respective password)  not allow to load correctly to URL (or google chrom, firefox or Internet Explorer)

My question is how to delete these configuration.